Does it weaken the theory?
Proc Natl Acad Sci U S A 1998 Dec
8;95(25):14763-8
Telomerase expression in chickens: constitutive activity in somatic
tissues and
down-regulation in culture.
Venkatesan RN, Price C
Department of Chemistry and Department of Biochemistry, N146 Beadle,
University of Nebraska, Lincoln, NE 68588, USA.
[Medline record in process]
Although human and rodent telomeres have been studied extensively, very
little is known about telomere dynamics in other vertebrates. Moreover,
our
current dependence on mice as a model for human tumorigenesis and aging
poses a problem because human and mouse telomere biology is very
different. To explore whether chickens might provide a more useful model,
we have examined telomerase activity and telomere length in chicken
tissues as well as in primary cell cultures. Although chicken telomeres
resemble human telomeres in that they are 8-20 kb in length, the
distribution of
telomerase activity in chickens resembles what is found in mice. Active
enzyme is present in germline tissue as well as in a wide range of somatic
tissues. Because chicken cells exhibit extremely low rates of spontaneous
immortalization, this finding indicates that constitutive telomerase
expression
does not necessarily lead to an increased immortalization frequency.
Finally, we found that telomerase activity is greatly down-regulated when
primary
cultures are established from chicken embryos. Although this
down-regulation explains the telomere loss and replicative senescence that
we observed
in fibroblast cultures, it raises questions concerning how relevant
studies of senescence in primary cell cultures are to aging in whole
animals.
_______________________________________________________________________________
Tony Benjamin Csoka, Ph.D.
Tel: (415) 476 2745
Fax: (415) 476 9672
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